فهرست مطالب s. khatib

This study focuses on density and species composition of phytoplankton during bloom in the southwestern Caspian Sea off Anzali. The eighteen sampls were took  between Apri and July 2021. The findings displayed, the  phytoplankton bloom speices was distanguited in the study as cyanobacteria Nodularia spumigena  Mertens as bloom in the southwestern Caspian Sea in 2005. A total of 8  phytoplankton species were distinguished during the bloom, the phytoplankton abundance were calculated  as 8,640,000 cells.l-1. Contributions of cyanophyta (5,720,000 cells. l-1) to total phytoplankton were higher than any other group. The cyanobacteria Nodularia spumigena abundance as 512,000,000 cells.l-1 provided the biggest contributions to the total phytoplankton during the bloom. Vertical distribution of  N. spumigena at the bloom region revealed that most N. spumigena abundance occurred in the upper layer (0-5 m) almost 5,000,000 cells.l-1. After bloom period, the number of phytoplankton species increased sharply and identified 18 species. Bacillariophyta were dominant (60,000 cells.l-1). Cyanobacteria (12,600 cells.l-1) were the second most important group, contributing to the total phytoplankton abundance. The phtytoplankton abundance was declined  sharply almost 83,400 cells.l-1 after bloom as compared with bloom period. The total phosphorus and nitrogen consenterations rised sharply as 0.59  and 9.91 µM. l-1 during bloom. There is strong relationship between N. spumigena abundance and environments factors. The very low wind, strong heating of the upper layer almost 29 ºC and increasing of  nutrients levels were the most reasons of N. spumigena bloom in the southwestern Caspain Sea Anzali offshore.

Water hyacinth (Eichhornia crassipes) is native to the Amazon basin and is one of the worst aquatic weeds in the world. It has been an invasive species in aquatic ecosystems of northern Iran since 2011. The use of herbicides as a method of plant control is common and efforts are made to select a formulation with the least impact on the environment. In the current study, three types of herbicide including glyphosate (Roundup), Glufosinate-ammonium (Basta) and Bispyribac sodium (Nominee) were used to control water hyacinth and the effects of their use on the abundance and diversity of planktonic communities were investigated. Roundup treatment has an immediate effect on water hyacinth, while Basta and Nominee treatments were effective for a longer period of time. Results showed that about 90% of phytoplankton and 71% of zooplankton belonged to the diatom and protozoa, respectively. The diversity of plankton species did not change after herbicides application and the number of genera in control ponds was almost constant. The phytoplankton abundance was higher after herbicides applications, especially in the Roundup treatment. The used doses of herbicides not only had a controlling effect on water hyacinth but also had no significant negative effect on the diversity and abundance of planktonic communities.

In this study the biotic and abiotic characteristics of Ardalan dam reservoir was studied from 2011 to 2012. Diatoms, Bacillariophyta, was the main phylum of phytoplankton in Ardalan dam reservoir that was dominant in the most seasons and green algae, Chlorophyta, was the second dominance groups. Survey of zooplanktons showed there were 25 genus from 6 phylum, and Rotatoria constitute 64% of the zooplanktons in. The average phytoplankton and zooplankton abundance during this study were about 19.15×106 and 1863 per liter of lake water respectively. Survey of benthic communities showed that Chironomidae and Tubificidae were the main benthic groups in Ardalan dam. Average of benthic biomass during this survey was 0.9 gr/m2 which is very poor. Sediments in Ardalan dam was mostly of silt and clay. Fish structure survey by gill nets in Ardalan dam showed that common carp and silver carp, by %53 and %45 respectively were the main economical species in the dam. Hydro chemical survey showed that total phosphorus and total nitrogen were 0.073 and 0.779 mg/L respectively. The amount of chlorophyll a was 6.03 mg/m3. The range `of dissolved oxygen was 6.4-10.5 mg/L. Average of EC was 576 µs/cm. Since the water temperature just in august month was more than 20ºC, the appropriate period for warm water fish culture in this reservoir is limited